The present invention relates generally to compounds and methods for utilizing soils found in place as materials of construction in the fabrication and erection of homes, offices, apartments, condominiums and commercial structures as an economical substitute for lumber, bricks, concrete blocks, poured concrete, lath and plaster, dry wall gypsum board, fiberboard, chip board, masonite and to some degree at least, various insulating materials such as fiberglass, rock wool, cellulose and various foamed materials. That many of these materials are now in very short supply and that their prices are continually escalating has been pointed out in my co-pending patent application entitled: Improved Earthen Cement Compositions for Building Materials and Process, Ser. No. 928,798, filed July 28, 1978. In that application the severe limitations placed upon the use of soils as construction materials was described. While the compounds and methods encompassed therein did constitute a major and important step in promoting a new state of the art of utilizing soils in the construction of homes and buildings, the need for an earthen composition that would be inherently waterproof and that would make use of less expensive cementing agents led to the development of the methods and compounds described subsequently in this application.
For thousands of years man has built structures of soil, and even today such buildings are constructed in many countries, especially in the less industrialized areas. Usually soils are only successfully used as construction materials where the climate is hot and dry and where the soil is of the class commonly known as adobe. In the United States the area in which adobe or rammed earth structures are permitted by building codes is limited to the southwestern part of the country, extending from Texas to Southern California and northward as far as central Colorado. While straw, manure and pine needles were often blended into sun-dried adobe blocks in the past, uniform and local building codes today prohibit the inclusion of more than 0.5% organic matter and not more than 0.3% soluable salts in the composition of such blocks. In addition, the clay used in unburned brick masonry must be blended with more coarsely graded soils such as sand before being utilized for such purposes.
A typical ASTM composition specification will contain from 55%-75% sand and 25%-45% silt and clay. Not more than 10% may be retained on a No. 1 sieve; not less than 25% nor more than 50% can pass a No. 200 mesh sieve; and the soil must have a plasticity index not less than 2 nor more than 15. Stabilizers such as Portland cement, lime and asphalt, either quick drying cutback or emulsion are used. The bricks must be sealed with a water repellant chemical so as not to absorb more than 21/2% by weight of water when placed upon a constantly water saturated surface for seven days. Typical strength requirements are as follows: Compressive strength average of 300 psi on 5 masonry units with minimum of 250 psi on any one; absorption maximum of 21/2% seven days exposure of one face; modulus of rupture minimum of 50 psi on average of 5 masonry units with tolerance of 30 psi for one unit; erosion maximum of 1/16-inch deep when subjected to 20 psi pressure water spray.
The use of unburned masonry bricks in cool rainy climates is usually prohibited by local building codes even if they are produced in accordance with ASTM or UBC standards. While it is one of the purposes of this invention to make possible the production and use of unfired masonry bricks in any part of the United States including areas of high rainfall and frequent freeze and thaw cycles, another purpose is the improvement of the state of the art of tamping earthen compositions into forms so as to be able to economically construct solid exterior and interior walls.
The chemicals employed under my co-pending patent application Ser. No. 928,798 operate in the hydroxide phase, preferably at a pH in excess of 12.5. On the other hand, the cemented compositions described herein are achieved in the acid phase by momentarily reducing the pH to a point below 2.0 and preferably at or near 1.0 to 1.2. It represents an extension of the state of the art of sulfonic acid stabilization and utilization as taught by my U.S. Pat. No. 3,876,439 entitled Soil Stabilizing Agent Comprising an Acid Sludge-Sulfuric Acid Product and Method for Preparing the Agent and my co-pending patent application Ser. No. 923,799 entitled Acidic Asphaltic Composition and Method.
My aforesaid U.S. Pat. No. 3,876,439 teaches that a soil stabilizing agent consisting of a source of calcium, such as calcium carbonate, and a spent sulfuric acid, along with certain ancillary components, can stabilize finely divided soils, reduce erosion and eliminate problems usually associated with frost heaving or lensing. Its effectiveness is primarily due to the reduction in moisture content that any clay or silt will demonstrate after treatment. However, the strength of the cemented bonds within the soil structure are not such as to achieve the compressive strength required for use in building structures above ground even if used at the maximum rate recommended. Also, the ability of water to freely enter and leave the structure does not recommend it for such purposes.
My co-pending patent application Ser. No. 923,799 demonstrates that dilute aqueous solutions of a sulfonic acid when used in conjunction with paving aggregates and asphalt will make possible the reduction of the use of asphaltic concrete by from 10%-40% while achieving comparable strength and durability when compared with standard paving compositions. It further teaches that paving asphalts may be applied to rock, gravel, sand and soils present in the roadbed in conjunction with heat, hot water or steam and a sulfonic acid source so as to achieve compositions satisfactory for use as either paving materials or asphalt stabilized base. However, while a waterproof composition is readily achieved by utilizing the process described therein when the type of aggregate suitable for paving materials is present, a composition satisfactory as a material of construction in buildings cannot be produced from in place soils even at the maximum rates of sulfonic acid and asphalt usage described therein.
While sulfonic acids used in conjunction with sources of calcium in accordance with my U.S. Pat. No. 3,876,439 or with paving asphalt as specified in my copending patent application Ser. No. 923,799 do not provide a composition suitable for use as a building material when combined with clays, silts, loams or sands usually found at a building site, suitable compoditions can be achieved by incorporating one or more of the constituents mentioned in my co-pending patent application Ser. No. 928,798 and concurrently adjusting the rate of usage of sulfonic acids, sources of calcium and asphalt as detailed subsequently in this application. Other cementing agents that will provide higher bonding strength may be used as hereinafter described. In addition, a desirable alteration in the basic energy capacity and energy resistance of typical soils may be achieved in a manner similar to that described in my co-pending patent application Ser. No. 928,798.